1. Field of the Invention
This invention generally relates to an image processing method and device and, more particularly, to a locus smoothing method and a navigation device using the same.
2. Description of the Related Art
Present interactive image systems have widely used a navigation device, such as a mouse or a pointing device, to estimate displacement, which will then be transmitted to an image display. In this manner, a user can manipulate the navigation device to correspondingly control the movement of a cursor or an aiming point shown on the image display. However, because the displacement estimated and output by the navigation device is a quantified value, if the quantified value is not processed by a smoothing process, the displacement output by the navigation device generally appears jagged appearance. When a user manipulates the navigation device to perform such as a drawing operation, it may not be easy to perform precise drawing that the user desires.
Therefore, the field of art provides locus smoothing methods in an attempt to solve aforementioned problem. For example, U.S. Pat. No. 5,661,502, entitled “Self-adjusting Digital Filter for Smoothing Computer Mouse Movement,” provides a pointer movement smoothing method using a computer program. The method includes the steps of: determining current device coordinates of an input device; determining previous device coordinates of the pointer device; determining a value of an inertial constant; calculating corrected device coordinates using the current device coordinates, the previous device coordinates and the inertial constant; and outputting the corrected device coordinates to a display for displaying; wherein the value of the inertial constant is dependent upon a value of a constant indicative of a desired amount of speed sensitivity, the speed of movement of the input device, and a value of a constant indicative of a desired amount of filtering. In conclusion, the above method performs smoothing process based on current coordinates and previous corrected coordinates of the input device, so it has a limited smoothing effect. In addition, if it is desired to use the method to accumulate more previous information to obtain a better smoothing effect, a large memory space is required to record a variety of information, and thus a higher memory cost is unavoidable.
Accordingly, the present invention further provides a method and a navigation device using the same that performs locus smoothing according to an accumulation of a predetermined number of displacement information. A digital filter formed according to the locus smoothing method of the present invention has better smoothing effect and only needs to record the accumulation of previous displacement information. Since the accumulation of previous displacement information already includes all information of previous displacements, it is not necessary to spend large memory resources recording all displacement information separately and thus the system cost can be reduced.